Sense amplifier having offset cancellation

ABSTRACT

A sense amplifier includes a sense amplifying unit, first and second isolation units, and first and second offset cancellation unit. The sense amplifying unit includes a first P-type metal-oxide-semiconductor (PMOS) transistor, a second PMOS transistor, a first N-type metal-oxide-semiconductor (NMOS) transistor, and a second NMOS transistor. In a layout of the sense amplifier, the first and second PMOS transistors are disposed in a central region of the sense amplifier, the first and second NMOS transistors are disposed at opposite sides of the sense amplifier from each other, the first isolation unit and the first offset cancellation unit are disposed between the first PMOS transistor and the first NMOS transistor, and the second isolation unit and the second offset cancellation unit are disposed between the second PMOS transistor and the second NMOS transistor. In other layouts, the locations of the PMOS transistors and NMOS transistors may be reversed.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Continuation of U.S. application Ser. No. 16/989,207, filedAug. 10, 2020, which is a Continuation of U.S. application Ser. No.16/829,044, filed Mar. 25, 2020, now U.S. Pat. No. 10,803,925, issuedOct. 13, 2021, which is a Continuation of U.S. application Ser. No.16/707,738, filed Dec. 9, 2019, now U.S. Pat. No. 10,692,565, issuedJun. 23, 2020, which is a Continuation of U.S. application Ser. No.16/256,883, filed Jan. 24, 2019, now U.S. Pat. No. 10,541,022, issuedJan. 21, 2020, which is a Continuation of U.S. application Ser. No.15/697,164, filed Sep. 6, 2017, now U.S. Pat. No. 10,224,093, issuedMar. 5, 2019, and a claim of priority is made to Korean PatentApplication No. 10-2016-0181446, filed on Dec. 28, 2016, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND

The inventive concept relates to a semiconductor memory device, and moreparticularly, to a sense amplifier for improving an effective sensingmargin based on an operation of cancelling an offset of the senseamplifier.

A dynamic random-access memory (DRAM) among memory devices operates in amanner in which data is written by electric charges stored in cellcapacitors of memory cells. Memory cells are connected to a bit line(BL) and a complementary bit line (BLB). In a DRAM, when a readoperation or a refresh operation is performed, a sense amplifier sensesand amplifies a voltage difference between the bit line and thecomplementary bit line. Semiconductor devices constituting the senseamplifier may have different device characteristics, for example,different threshold voltages, due to a process variation, temperature,or the like. Such different device characteristics may cause offsetnoise in the sense amplifier. Due to the offset noise, an effectivesensing margin of the sense amplifier may be reduced, and performance ofthe DRAM may be reduced.

SUMMARY

The inventive concept provides a sense amplifier which may improve aneffective sensing margin based on an operation of cancelling an offsetof the sense amplifier, and a layout method thereof.

According to an aspect of the inventive concept, there is provided asense amplifier which senses a voltage variation of a bit line. Thesense amplifier includes a sense amplifying unit connected to the bitline and a complementary bit line, configured to sense a voltagevariation of the bit line in response to a first control signal and asecond control signal, and configured to adjust voltages of a sensingbit line and a complementary sensing bit line based on the sensedvoltage variation, a first isolation unit configured to connect the bitline to the sensing bit line in response to an isolation signal, asecond isolation unit configured to connect the complementary bit lineto the complementary sensing bit line in response to the isolationsignal, a first offset cancellation unit configured to connect the bitline to the complementary sensing bit line in response to an offsetcancellation signal, and a second offset cancellation unit configured toconnect the complementary bit line to the sensing bit line in responseto the offset cancellation signal. The sense amplifying unit includes afirst P-type metal-oxide-semiconductor (PMOS) transistor connectedbetween the first control signal and the complementary sensing bit lineand having a gate connected to the sensing bit line, a second PMOStransistor connected between the first control signal and the sensingbit line and having a gate connected to the complementary sensing bitline, a first N-type metal-oxide-semiconductor (NMOS) transistorconnected between the second control signal and the complementarysensing bit line and having a gate connected to the bit line, and asecond NMOS transistor connected between the second control signal andthe sensing bit line and having a gate connected to the complementarybit line

In the sense amplifier according to embodiments of the inventiveconcept, the first and second PMOS transistors are disposed in a centralregion of the sense amplifier, the first and second NMOS transistors arerespectively disposed at both edges of the sense amplifier, the firstisolation unit and the first offset cancellation unit are disposedbetween the first PMOS transistor and the first NMOS transistor, and thesecond isolation unit and the second offset cancellation unit aredisposed between the second PMOS transistor and the second NMOStransistor.

In the sense amplifier according to embodiments of the inventiveconcept, the first and second NMOS transistors are disposed in a centralregion of the sense amplifier, the first and second PMOS transistors arerespectively disposed at both edges of the sense amplifier, the firstisolation unit and the first offset cancellation unit are disposedbetween the first NMOS transistor and the first PMOS transistor, and thesecond isolation unit and the second offset cancellation unit aredisposed between the second NMOS transistor and the second PMOStransistor.

According to another aspect of the inventive concept, a devicecomprises: an isolation transistor configured to connect a bit line to asensing bit line in response to an isolation signal; an offsetcancellation transistor configured to connect the bit line to acomplementary sensing bit line in response to an offset cancellationsignal; and a sense amplifying unit configured to sense a bit linevoltage of the bit line, the sense amplifying unit including a P-typemetal oxide semiconductor (PMOS) transistor and an N-type metal oxidesemiconductor (NMOS) transistor. The isolation transistor and the offsetcancellation transistor are disposed between the PMOS transistor and theNMOS transistor.

According to yet another aspect of the inventive concept, a senseamplifier comprises: a first isolation unit configured to connect a bitline to a sensing bit line in response to an isolation signal; a secondisolation unit configured to connect a complementary bit line to acomplementary sensing bit line in response to the isolation signal; afirst offset cancellation unit configured to connect the bit line to thecomplementary sensing bit line in response to an offset cancellationsignal; a second offset cancellation unit configured to connect thecomplementary bit line to the sensing bit line in response to the offsetcancellation signal; a pair of P-type metal oxide semiconductor (PMOS)transistors, including, a first PMOS transistor connected between afirst control line and the complementary sensing bit line, and having acontrol terminal connected to the sensing bit line, and a second PMOStransistor connected between the first control line and the sensing bitline, and having a control terminal connected to the complementarysensing bit line; and a pair of N-type metal oxide semiconductor (NMOS)transistors, including, a first NMOS transistor connected between asecond control line and the complementary sensing bit line, and having acontrol terminal connected to the sensing bit line, and a second NMOStransistor connected between the second control line and the sensing bitline, and having a control terminal connected to the complementarysensing bit line. First transistors of a first pair selected from thepair of PMOS transistors and the pair NMOS transistors are disposed atopposite sides of the sense amplifier from each other, and secondtransistors of a second pair selected from the pair of PMOS transistorsand the pair NMOS transistors are disposed in a central region of thesense amplifier between the first transistors. The first isolation unitand the first offset cancellation unit are disposed between the firstPMOS transistor and the first NMOS transistor. The second isolation unitand the second offset cancellation unit are disposed between the secondPMOS transistor and the second NMOS transistor.

According to still another aspect of the inventive concept, a memorydevice comprises: a first memory cell array having a bit line; a secondmemory cell array having a complementary bit line; and a sense amplifierfor sensing a bit line voltage of the bit line. The sense amplifiercomprises: a first isolation unit configured to connect the bit line toa sensing bit line in response to an isolation signal; a secondisolation unit configured to connect the complementary bit line to acomplementary sensing bit line in response to the isolation signal; afirst offset cancellation unit configured to connect the bit line to thecomplementary sensing bit line in response to an offset cancellationsignal; a second offset cancellation unit configured to connect thecomplementary bit line to the sensing bit line in response to the offsetcancellation signal; a pair of P-type metal oxide semiconductor (PMOS)transistors, including, a first PMOS transistor connected between afirst control line and the complementary sensing bit line, and having acontrol terminal connected to the sensing bit line, and a second PMOStransistor connected between the first control line and the sensing bitline, and having a control terminal connected to the complementarysensing bit line; and a pair of N-type metal oxide semiconductor (NMOS)transistors, including, a first NMOS transistor connected between asecond control line and the complementary sensing bit line, and having acontrol terminal connected to the sensing bit line, and a second NMOStransistor connected between the second control line and the sensing bitline, and having a control terminal connected to the complementarysensing bit line. Transistors of a first pair selected from the pair ofPMOS transistors and the pair NMOS transistors are disposed at oppositesides of the sense amplifier from each other, and transistors of asecond pair selected from the pair of PMOS transistors and the pair NMOStransistors are disposed in a central region of the sense amplifierbetween the transistors of the first pair. The first isolation unit andthe first offset cancellation unit are disposed between the first PMOStransistor and the first NMOS transistor. The second isolation unit andthe second offset cancellation unit are disposed between the second PMOStransistor and the second NMOS transistor.

According to a further aspect of the inventive concept, a senseamplifier comprises: a first isolation unit configured to connect a bitline to a sensing bit line in response to an isolation signal; a secondisolation unit configured to connect a complementary bit line to acomplementary sensing bit line in response to the isolation signal; afirst offset cancellation unit configured to connect the bit line to thecomplementary sensing bit line in response to an offset cancellationsignal; a second offset cancellation unit configured to connect thecomplementary bit line to the sensing bit line in response to the offsetcancellation signal; a first P-type metal oxide semiconductor (PMOS)transistor connected between a first control line and the complementarysensing bit line and having a control terminal connected to the sensingbit line; a second PMOS transistor connected between the first controlline and the sensing bit line and having a control terminal connected tothe complementary sensing bit line; a first N-type metal oxidesemiconductor (NMOS) transistor connected between a second control lineand the complementary sensing bit line and having a control terminalconnected to the sensing bit line; and a second NMOS transistorconnected between the second control line and the sensing bit line andhaving a control terminal connected to the complementary sensing bitline. The first isolation unit and the first offset cancellation unitare disposed between the first PMOS transistor and the first NMOStransistor. The second isolation unit and the second offset cancellationunit are disposed between the second PMOS transistor and the second NMOStransistor. Either: the NMOS transistors are disposed at opposite sidesof the sense amplifier from each other, and the PMOS transistors aredisposed in a central region of the sense amplifier between the NMOStransistors, or the PMOS transistors are disposed at the opposite sidesof the sense amplifier from each other, and the NMOS transistors aredisposed in the central region of the sense amplifier between the PMOStransistors.

According to a yet further aspect of the inventive concept, a senseamplifier comprises: a first isolation unit configured to selectivelyconnect a bit line to a sensing bit line; a second isolation unitconfigured to selectively connect a complementary bit line to acomplementary sensing bit line; a first offset cancellation unitconfigured to selectively connect the bit line to the complementarysensing bit line; a second offset cancellation unit configured toselectively connect the complementary bit line to the sensing bit line;a first P-type metal oxide semiconductor (PMOS) transistor configured toselectively connect a first control line and the complementary sensingbit; a second PMOS transistor configured to selectively connect thefirst control line and the sensing bit line; a first N-type metal oxidesemiconductor (NMOS) configured to selectively connect a second controlline and the complementary sensing bit line; and a second NMOStransistor configured to selectively connect the second control line andthe sensing bit line. The first isolation unit and the first offsetcancellation unit are disposed between the first PMOS transistor and thefirst NMOS transistor. The second isolation unit and the second offsetcancellation unit are disposed between the second PMOS transistor andthe second NMOS transistor. Either: the NMOS transistors are disposed atopposite sides of the sense amplifier from each other, and the PMOStransistors are disposed in a central region of the sense amplifierbetween the NMOS transistors, or the PMOS transistors are disposed atthe opposite sides of the sense amplifier from each other, and the NMOStransistors are disposed in the central region of the sense amplifierbetween the PMOS transistors.

According to a still further aspect of the inventive concept, a senseamplifier comprises: a first isolation unit; a second isolation unit; afirst offset cancellation unit; a second offset cancellation unit; apair of P-type metal oxide semiconductor (PMOS) transistors including afirst PMOS transistor and a second PMOS transistor; and a pair of N-typemetal oxide semiconductor (NMOS) transistors including a first NMOStransistor and a second NMOS transistor. Transistors of a first pairselected from the pair of PMOS transistors and the pair NMOS transistorsare disposed at opposite sides of the sense amplifier from each other,and transistors of a second pair selected from the pair of PMOStransistors and the pair NMOS transistors are disposed in a centralregion of the sense amplifier between the transistors of the first pair.The first isolation unit and the first offset cancellation unit aredisposed between the first PMOS transistor and the first NMOStransistor. The second isolation unit and the second offset cancellationunit are disposed between the second PMOS transistor and the second NMOStransistor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the inventive concept will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings,

FIG. 1 is a block diagram for describing an embodiment of a memorydevice.

FIGS. 2A and 2B are diagrams for describing a bit line voltage sensingoperation of a sense amplifier of FIG. 1 .

FIG. 3 is a circuit diagram for describing an embodiment of a senseamplifier.

FIGS. 4, 5, 6A, 6B, 6C, 6D, 6E and 7 are circuit diagrams and aflowchart for describing operations of the sense amplifier illustratedin FIG. 3 .

FIG. 8 is a timing diagram for describing the operations of the senseamplifier of FIG. 3 .

FIG. 9 is a diagram illustrating an example embodiment of a memorydevice to which example embodiments of a sense amplifier as describedherein is applied.

FIGS. 10, 11, 12, 13, 14, 15, 16 and 17 are diagrams for describingembodiments of layouts and layout methods of a sense amplifier.

FIG. 18 is a circuit diagram for describing another embodiment of asense amplifier.

FIGS. 19 and 20 are diagrams for describing embodiments of layouts andlayout methods of the sense amplifier of FIG. 18 .

FIG. 21 is a circuit diagram for describing still another embodiment ofa sense amplifier.

FIGS. 22 and 23 are diagrams for describing embodiments of layouts andlayout methods of the sense amplifier of FIG. 21 .

FIGS. 24 and 25 are diagrams illustrating example embodiments of amemory device to which a sense amplifier according to the embodimentsdescribed herein may be applied.

FIG. 26 is a block diagram illustrating an example in which a memorydevice including a sense amplifier according to the embodimentsdescribed herein is applied to a mobile device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the inventive concept will be described withreference to the accompanying drawings. However, it will be understoodby those skilled in the art that the inventive concept may be performedin other concrete forms without changing the technological scope andessential features. Therefore, embodiments described below should beconsidered in a descriptive sense only and not for purposes oflimitation.

As is traditional in the field of the inventive concepts, one or moreelements of embodiments may be described and illustrated in terms offunctional blocks, units and/or modules. These blocks, units and/ormodules are physically implemented by electronic circuits such as logiccircuits, microprocessors, hard-wired circuits or the like, and mayoptionally be driven by firmware and/or software. Also, each functionalblock, unit and/or module of the embodiments may be physically separatedinto two or more interacting and discrete blocks, units and/or moduleswithout departing from the scope of the inventive concepts. Further, twoor more of the functional blocks, units and/or modules of theembodiments may be physically combined into more complex blocks or unitswithout departing from the scope of the inventive concepts.

FIG. 1 is a block diagram for describing an embodiment of a memorydevice.

Referring to FIG. 1 , a memory device 100 may be a storage unit ordevice based on semiconductor devices or components. For example, memorydevice 100 may be a volatile memory such as a dynamic random-accessmemory (DRAM), a synchronous dynamic random-access memory (SDRAM), adouble data rate synchronous dynamic random-access memory (DDR SDRAM), alow power double data rate synchronous dynamic random-access memory(LPDDR SDRAM), a graphics double data rate synchronous dynamicrandom-access memory (GDDR SDRAM), a double data rate type twosynchronous dynamic random-access memory (DDR2 SDRAM), a double datarate type three synchronous dynamic random-access memory (DDR3 SDRAM), adouble data rate fourth-generation synchronous dynamic random-accessmemory (DDR4 SDRAM), a thyristor random-access memory (TRAM), or thelike, or a non-volatile memory such as a phase-change random-accessmemory (PRAM), a magnetic random-access memory (MRAM), a resistiverandom-access memory (RRAM), or the like.

Memory device 100 may output data through data lines DQ in response tocommands CMD, addresses ADDR, and control signals, which are receivedfrom an external device, for example, a memory controller. Memory device100 includes a memory cell array 110, a command decoder 112, a controllogic 114, an address buffer 120, a row decoder 130, a column decoder140, a sense amplifier 150, and a data input-and-output circuit 160.

Memory cell array 110 includes a plurality of memory cells which areprovided in a matrix form arranged in rows and columns. Memory cellarray 110 includes a plurality of word lines and a plurality of bitlines BL, which are connected to the memory cells. The plurality of wordlines may be connected to rows of the memory cells and the plurality ofbit lines BL may be connected to columns of the memory cells.

Command decoder 112 may decode a write enable signal/WE, a row addressstrobe signal/RAS, a column address strobe signal/CAS, a chip selectsignal/CS, and the like, which are received from the external device,for example, the memory controller, and may allow control logic 114 togenerate control signals corresponding to commands CMD. The commands CMDmay include an activate command, a read command, a write command, aprecharge command, and the like.

Address buffer 120 receives addresses ADDR from the memory controller,which is an external device. The addresses ADDR include a row address RAwhich addresses a row of memory cell array 110 and a column address CAwhich addresses a column of memory cell array 110. Address buffer 120may transmit the row address RA to row decoder 130 and the columnaddress CA to column decoder 140.

Row decoder 130 may select any one of the plurality of word linesconnected to memory cell array 110. Row decoder 130 may decode the rowaddress RA received from address buffer 120, select any one word linecorresponding to the row address RA, and activate the selected wordline.

Column decoder 140 may select a predetermined number of bit lines fromthe plurality of bit lines BL of memory cell array 110. Column decoder140 may decode the column address CA received from address buffer 120and select a predetermined number of bit lines BL corresponding to thereceived column address CA.

Sense amplifier 150 is connected to the bit lines BL of memory cellarray 110. Sense amplifier 150 may sense a variation of voltages of theselected bit lines among the plurality of bit lines BL, amplify thevoltage variations, and output the amplified voltage variations. Datainput-and-output circuit 160 may output data, based on the voltagessensed and amplified by sense amplifier 150, through the data lines DQ.

Sense amplifier 150 may receive an isolation signal ISO and an offsetcancellation signal OC from control logic 114. Sense amplifier 150 mayperform an offset cancelling operation in response to the isolationsignal ISO and the offset cancellation signal OC. For example, an offsetindicates a characteristic difference between semiconductor devicesconstituting sense amplifier 150, for example, a difference betweenthreshold voltages of different semiconductor devices.

Hereinafter, a configuration and operations of sense amplifier 150 willbe described in detail with reference to various embodiments.

FIGS. 2A and 2B are diagrams for describing a bit line voltage sensingoperation of the sense amplifier of FIG. 1 .

Referring to FIGS. 1 and 2A, a memory cell MC included in memory cellarray 110 includes a cell transistor 21 and a cell capacitor 22. Memorydevice 100 may perform a read operation or a refresh operation based onan amount of electric charge stored in the cell capacitor 22 included inthe memory cell MC. In this case, a bit line BL connected to the memorycell MC is precharged to a precharge voltage Vpre. Then, as the wordline WL is activated, a charge sharing operation is performed betweenelectric charges of the bit line BL charged to the precharge voltageVpre and electric charges of cell capacitor 22 of the memory cell MC.Due to the charge sharing operation, a voltage of the bit line BL may bedecreased or increased from the precharge voltage Vpre by an amount of avoltage variation (ΔV).

Sense amplifier 150 may sense the amount of voltage variation (ΔV) andamplify the amount thereof. In this case, due to a bit line couplingnoise, a sense amplifier offset noise, and the like, an effectivesensing margin of sense amplifier 150 may be represented as illustratedin FIG. 2B. When the amount of voltage variation (ΔV) is less than orequal to a predetermined level, sense amplifier 150 may not sense theamount of voltage variation (ΔV) of the bit line BL. That is, the senseamplifier offset noise may be a factor that reduces the effectivesensing margin of sense amplifier 150.

FIG. 3 is a circuit diagram for describing an embodiment of a senseamplifier.

Referring to FIG. 3 , a sense amplifier 150 includes first and secondisolation units 151 and 152, first and second offset cancellation units153 and 154, and a sense amplifying unit 155.

First isolation unit 151 is connected between a bit line BL and asensing bit line SABL and second isolation unit 152 is connected betweena complementary bit line BLB and a complementary sensing bit line SABLB.First and second isolation units 151 and 152 receive isolation signalsISO and operate in response to the isolation signals ISO.

First isolation unit 151 may include a first isolation transistor ISO_1which connects the bit line BL and the sensing bit line SABL, orisolates the bit line BL from the sensing bit line SABL, in response tothe isolation signal ISO. One terminal of the first isolation transistorISO_1 is connected to the bit line BL, the other terminal thereof isconnected to the sensing bit line SABL, and a gate thereof is connectedto the isolation signal ISO.

Second isolation unit 152 may include a second isolation transistorISO_2 which connects the complementary bit line BLB and thecomplementary sensing bit line SABLB, or isolates the complementary bitline BLB from the complementary sensing bit line SABLB, in response tothe isolation signal ISO. One terminal of the second isolationtransistor ISO_2 is connected to the complementary bit line BLB, theother terminal thereof is connected to the complementary sensing bitline SABLB, and a gate thereof is connected to the isolation signal ISO.

First offset cancellation unit 153 is connected between the bit line BLand the complementary sensing bit line SABLB, and second offsetcancellation unit 154 is connected between the complementary bit lineBLB and the sensing bit line SABL. First and second offset cancellationunits 153 and 154 receive offset cancellation signals OC and operate inresponse to the offset cancellation signals OC.

First offset cancellation unit 153 may include a first offsetcancellation transistor OC_1 which connects the bit line BL and thecomplementary sensing bit line SABLB, or disconnects the bit line BLfrom the complementary sensing bit line SABLB, in response to the offsetcancellation signal OC. One terminal of the first offset cancellationtransistor OC_1 is connected to the bit line BL, the other terminalthereof is connected to the complementary sensing bit line SABLB, and agate thereof is connected to the offset cancellation signal OC.

Second offset cancellation unit 154 may include a second offsetcancellation transistor OC_2 which connects the complementary bit lineBLB and the sensing bit line SABL, or disconnects the complementary bitline BLB from the sensing bit line SABL, in response to the offsetcancellation signal OC. One terminal of the second offset cancellationtransistor OC_2 is connected to the complementary bit line BLB, theother terminal thereof is connected to the sensing bit line SABL, and agate thereof is connected to the offset cancellation signal OC.

Sense amplifying unit 155 may be connected between the sensing bit lineSABL and the complementary sensing bit line SABLB, and may sense andamplify a voltage difference between the bit line BL and thecomplementary bit line BLB in response to first and second controlsignals LA and LAB. Sense amplifying unit 155 includes a pair of P-typemetal-oxide-semiconductor (PMOS) transistors, first and second PMOStransistors P_1 and P_2, and a pair of N-type metal-oxide-semiconductor(NMOS) transistors, first and second NMOS transistors N_1 and N_2.

One terminal of the first PMOS transistor P_1 is connected to thecomplementary sensing bit line SABLB, the other terminal thereof isconnected to a line of the first control signal LA, and a gate thereofis connected to the sensing bit line SABL. One terminal of the secondPMOS transistor P_2 is connected to the sensing bit line SABL, the otherterminal thereof is connected to the line of the first control signalLA, and a gate thereof is connected to the complementary sensing bitline SABLB.

One terminal of the first NMOS transistor N_1 is connected to thecomplementary sensing bit line SABLB, the other terminal thereof isconnected to a line of the second control signal LAB, and a gate thereofis connected to the bit line BL. One terminal of the second NMOStransistor N_2 is connected to the sensing bit line SABL, the otherterminal thereof is connected to the line of the second control signalLAB, and a gate thereof is connected to the complementary bit line BLB.

The bit line BL is connected to one terminal of cell transistor 21 (seeFIG. 2A) included in the memory cell MC. The word line WL is connectedto a gate of cell transistor 21.

FIGS. 4 to 7 are circuit diagrams and a flowchart for describingoperations of the sense amplifier illustrated in FIG. 3 .

FIG. 4 shows an equivalent circuit of sense amplifier 150 of FIG. 3 .For simplicity of the drawings, first and second isolation transistorsISO_1 and ISO_2 and first and second offset cancellation transistorsOC_1 and OC_2 are illustrated using dashed lines. Operations of theequivalent circuit of sense amplifier 150 illustrated in FIG. 4 will bedescribed in detail with reference to FIGS. 5 and 6A to 6E.

Referring to FIG. 5 , sense amplifier 150 of FIG. 4 may sequentiallyperform a pre-charging operation (S510), an offset cancelling operation(S520), a charge sharing operation (S530), a pre-sensing operation(S540), and a restoring operation (S550) in response to isolationsignals ISO, offset cancellation signals OC, and first and secondcontrol signals LA and LAB. For convenience of description, theoperations of FIG. 5 will be described with reference to FIGS. 6A to 6E.

Referring to FIG. 6A, in operation S510 of FIG. 5 , sense amplifier 150performs a pre-charging operation. Sense amplifier 150 precharges a bitline BL, a complementary bit line BLB, a sensing bit line SABL, and acomplementary sensing bit line SABLB to a precharge voltage Vpre. Forexample, the isolation signals ISO and the offset cancellation signalsOC may be logic high (H).

The first and second isolation transistors ISO_1 and ISO_2 and the firstand second offset cancellation transistors OC_1 and OC_2 are turned onin response to the isolation signals ISO and the offset cancellationsignals OC of logic high (H). Accordingly, the bit line BL, thecomplementary bit line BLB, the sensing bit line SABL, and thecomplementary sensing bit line SABLB may be connected to one node andcharged to the precharge voltage Vpre. In this case, the first andsecond control signals LA and LAB may be charged to the prechargevoltage Vpre.

Referring to FIG. 6B, in operation S520 of FIG. 5 , sense amplifier 150performs an offset cancelling operation. For example, the isolationsignals ISO may be logic low (L) and the offset cancellation signals OCmay be logic high (H).

The first and second isolation transistors ISO_1 and ISO_2 are turnedoff in response to the isolation signals ISO of logic low (L), and thefirst and second offset cancellation transistors OC_1 and OC_2 areturned on in response to the offset cancellation signals OC of logichigh (H). In this case, the first control signal LA is transitioned fromthe precharge voltage Vpre to an internal supply voltage VINTA and thesecond control signal LAB is transitioned from the precharge voltageVpre to a ground voltage VSS. The internal supply voltage VINTA may be avoltage supplied to memory cell array 110 (see FIG. 1 ). Then, the firstcontrol signal LA is transitioned from the internal supply voltage VINTAto the precharge voltage Vpre and the second control signal LAB istransitioned from the ground voltage VSS to the precharge voltage Vpre.

In sense amplifier 150, for example, the first and second PMOStransistors P_1 and P_2 and the first and second NMOS transistors N_1and N_2 may have different threshold voltages Vth than each other due toa variation in manufacturing processes, temperature, or the like. Inthis case, sense amplifier 150 may cause offset noise due to thedifference between the threshold voltages Vth of the first and secondPMOS transistors P_1 and P_2, and the first and second NMOS transistorsN_1 and N_2. Hereinafter, a method of compensating an offset of senseamplifier 150 through an offset cancelling operation will be describedwith reference to first to fourth examples.

In a first example (Case I), it is assumed that the threshold voltageVth of the first NMOS transistor N_1 is greater than the thresholdvoltage Vth of the second NMOS transistor N_2. The first and second NMOStransistors N_1 and N_2 operate as diodes. An amount of current whichflows through the first NMOS transistor N_1 may be less than an amountof current which flows through the second NMOS transistor N_2. Also, anamount of current which flows through the first PMOS transistor P_1 maybe less than an amount of current which flows through the second PMOStransistor P_2. Accordingly, as illustrated in FIG. 7 , the voltage onthe complementary bit line BLB may be increased to a predetermined levelwhich is greater than the voltage on the bit line BL.

In a second example (Case II), it is assumed that the threshold voltageVth of the second NMOS transistor N_2 is greater than the thresholdvoltage Vth of the first NMOS transistor N_1. The first and second NMOStransistors N_1 and N_2 operate as diodes. An amount of current whichflows through the second NMOS transistor N_2 may be less than an amountof current which flows through the first NMOS transistor N_1. Also, anamount of current which flows through the second PMOS transistor P_2 maybe less than an amount of current which flows through the first PMOStransistor P_1. Accordingly, as illustrated in FIG. 7 , the voltage onthe complementary bit line BLB may be reduced to a predetermined levelwhich is less than the voltage on the bit line BL.

In a third example (Case III), it is assumed that the threshold voltageVth of the first PMOS transistor P_1 is greater than the thresholdvoltage Vth of the second PMOS transistor P_2. An amount of currentwhich flows through the first PMOS transistor P_1 may be less than anamount of current which flows through the second PMOS transistor P_2.The first and second NMOS transistors N_1 and N_2 may flow apredetermined amount of current as diodes. Accordingly, as illustratedin FIG. 7 , the voltage on the complementary bit line BLB may beincreased to a predetermined level which is greater than the voltage onthe bit line BL.

In a fourth example (Case IV), it is assumed that the threshold voltageVth of the second PMOS transistor P_2 is greater than the thresholdvoltage Vth of the first PMOS transistor P_1. An amount of current whichflows through the second PMOS transistor P_2 may be less than an amountof current which flows through the first PMOS transistor P_1. The firstand second NMOS transistors N_1 and N_2 may flow a predetermined amountof current as diodes. Accordingly, as illustrated in FIG. 7 , thevoltage on the complementary bit line BLB may be reduced to apredetermined level which is less than the voltage on the bit line BL.

In the above-described first to fourth examples (Cases I to IV), thecomplementary bit line BLB is increased or decreased to thepredetermined level as compared to the bit line BL, and thus the bitline BL and the complementary bit line BLB have a predetermined voltagedifference. Such a voltage difference may be interpreted as an offsetvoltage due to the offset noise. This means that the offset noise ofsense amplifier 150 may be cancelled by causing the bit line BL and thecomplementary bit line BLB to have a difference by the offset voltage.That is, sense amplifier 150 may compensate for the offset through theoffset cancelling operation.

Referring to FIG. 6C, in operation S530 of FIG. 5 , sense amplifier 150performs a charge sharing operation. For example, the isolation signalsISO and the offset cancellation signals OC may be logic low (L).

The first and second isolation transistors ISO_1 and ISO_2 and the firstand second offset cancellation transistors OC_1 and OC_2 are turned offin response to the isolation signal ISO and the offset cancellationsignal OC of logic low (L). In this case, the word line WL connected tothe memory cell MC (see FIG. 3 ) is activated, and the charge sharingoperation is performed between electric charges stored in the cellcapacitor of the memory cell MC and electric charges stored in the bitline BL.

For example, when data having a value of ‘1’ is stored in the memorycell MC, a voltage level of the bit line BL may be increased by apredetermined amount during the charge sharing operation. On the otherhand, when data having a value of ‘0’ is stored in the memory cell MC,the voltage level of the bit line BL may be decreased by a predeterminedamount during the charge sharing operation.

Referring to FIG. 6D, in operation S540 of FIG. 5 , sense amplifier 150performs a pre-sensing operation. For example, the isolation signals ISOand the offset cancellation signals OC may be logic low (L).

When the charge sharing operation described in FIG. 6C is performed, thevoltage of the bit line BL may be increased or decreased by apredetermined amount (ΔV) according to the data stored in the memorycell MC. In this case, the first control signal LA is transitioned to aninternal supply voltage VINTA and the second control signal LAB istransitioned to a ground voltage VSS. Accordingly, sense amplifier 150may charge each of the voltages of the sensing bit line SABL and thecomplementary sensing bit line SABLB to the internal supply voltageVINTA and discharge each of the voltages of the sensing bit line SABLand the complementary sensing bit line SABLB to the ground voltage VSSbased on the voltage difference between the bit line BL and thecomplementary bit line BLB.

For example, when data having a value of ‘1’ is stored in the memorycell MC, the voltage on the sensing bit line SABL may be increased tothe internal supply voltage VINTA and the voltage on the complementarysensing bit line SABLB may be decreased to the ground voltage VSS duringthe pre-sensing operation. On the other hand, when data having a valueof ‘0’ is stored in the memory cell MC, the voltage on the sensing bitline SABL may be decreased to the ground voltage VSS and the voltage onthe complementary sensing bit line SABLB may be increased to theinternal supply voltage VINTA.

For example, during the pre-sensing operation, the bit line BL and thecomplementary bit line BLB, and the sensing bit line SABL and thecomplementary sensing bit line SABLB are disconnected from each other bythe first and second isolation transistors ISO 1 and ISO 2 and the firstand second offset cancellation transistors OC_1 and OC_2. As the senseamplifier 150 is separated from the bit line BL and the complementarybit line BLB, a coupling effect between the bit lines BL may be reducedand a sensing rate may be improved.

Referring to FIG. 6E, in operation S550 of FIG. 5 , sense amplifier 150performs a restoring operation. For example, the isolation signals ISOmay be logic high (H), and the offset cancellation signals OC may belogic low (L).

The first and second isolation transistors ISO_1 and ISO_2 are turned onin response to the isolation signals ISO of logic high (H), and thefirst and second offset cancellation transistors OC_1 and OC_2 areturned off in response to the offset cancellation signals OC of logiclow (L). In this case, the bit line BL and the sensing bit line SABL areconnected by the first isolation transistor ISO_1, and the complementarybit line BLB and the complementary sensing bit line SABLB are connectedby the second isolation transistor ISO_2. Accordingly, the voltage onthe bit line BL may be increased or decreased to a voltage level of thesensing bit line SABL, and the voltage on the complementary bit line BLBmay be increased or decreased to a voltage level of the complementarysensing bit line SABLB.

In some embodiments, a sensing bit line pair SABL and SABLB of senseamplifier 150 may be connected to a data line and data may be output toa local sense amplifier, a global sense amplifier, or the datainput-and-output circuit 160 (see FIG. 1 ) through the data line afterthe pre-sensing operation.

As described above, sense amplifier 150 performs the pre-chargingoperation, the offset cancelling operation, the charge sharingoperation, the pre-sensing operation, and the restoring operation basedon the isolation signals ISO, the offset cancellation signals OC, andthe first and second control signals LA and LAB. In this case, senseamplifier 150 may compensate for the offset of sense amplifier 150through the offset cancelling operation, minimize the coupling betweenthe bit lines through the pre-sensing operation, and thus an effectivesensing margin thereof may be improved. Accordingly, a sense amplifierhaving improved performance and a memory device including the same maybe provided.

FIG. 8 is a timing diagram for describing the operations of the senseamplifier of FIG. 3 . An X-axis of FIG. 8 denotes time and a Y-axisdenotes a signal level. For example, it is assumed that the memory cellMC stores data having a value of ‘1’ and a threshold voltage of thefirst NMOS transistor N_1 is greater than a threshold voltage of thefirst NMOS transistor N_2 by an offset voltage V_(OS).

Referring to FIG. 8 , sense amplifier 150 sequentially performs apre-charging operation, an offset cancelling operation, a charge sharingoperation, a pre-sensing operation, and a restoring operation.

In a first interval t0-t1, sense amplifier 150 performs a pre-chargingoperation. In this case, an isolation signal ISO and an offsetcancellation signal OC are at a logic high (H) level, and a bit linepair BL and BLB and a sensing bit line pair SABL and SABLB areprecharged to a precharge voltage Vpre.

In a second interval t1-t2, sense amplifier 150 performs an offsetcancelling operation. In this case, the isolation signal ISO becomeslogic low (L). A first control signal LA is increased from a prechargevoltage Vpre to an internal supply voltage VINTA and the second controlsignal LAB is reduced from a precharge voltage Vpre to a ground voltageVSS. sense amplifier 150 may perform the offset cancelling operationbased on the method described in FIGS. 5 and 6B. During the offsetcancelling operation, the voltage on complementary bit line BLB may begreater than the voltage on bit line BL by the offset voltage V_(OS).Accordingly, the voltages on the bit line BL and the complementary bitline BLB have a difference by the offset voltage V_(OS), and thus theoffset noise of sense amplifier 150 may be cancelled.

In a third interval t2-t3, sense amplifier 150 performs a charge sharingoperation. In this case, an isolation signal ISO and an offsetcancellation signal OC become logic low (L), the word line WL connectedto the memory cell MC is activated, and the charge sharing operation isperformed between electric charges stored in the cell capacitor of thememory cell MC and electric charges stored in the bit line BL. When datahaving a value of ‘1’ is stored in the memory cell MC, a voltage levelof the bit line BL may be increased by a predetermined level during thecharge sharing operation. In another embodiment, when data having avalue of ‘0’ is stored in the memory cell MC, the voltage level of thebit line BL may be reduced by a predetermined level during the chargesharing operation.

In a fourth interval t3-t4, sense amplifier 150 performs a pre-sensingoperation. In this case, the first control signal LA is transitioned tothe internal supply voltage VINTA and the second control signal LAB istransitioned to the ground voltage VSS. Accordingly, in sense amplifier150, the sensing bit line SABL is increased to the internal supplyvoltage VINTA and the complementary sensing bit line SABLB is reduced tothe ground voltage VSS, based on a voltage difference between the bitline BL and the complementary bit line BLB.

In a fifth interval t4-t5, sense amplifier 150 performs a restoringoperation. In this case, the isolation signal ISO becomes logic high (H)and first and second isolation transistors ISO_1 and ISO_2 are turnedon. The bit line pair BL and BLB and the sensing bit line pair SABL andSABLB are respectively connected to each other, and the bit line pair BLand BLB may be charged or discharged to the voltage level of the sensingbit line pair SABL and SABLB.

FIG. 9 is a diagram illustrating an example of a memory device to whicha sense amplifier according to embodiments described herein is applied.

Referring to FIG. 9 , a memory device 900 includes a plurality of memorycell arrays 110_1, 110_2, . . . to 110_n and a plurality of senseamplifiers 150_1, 150_2, . . . to 150_n. Each of the plurality of senseamplifiers 150_1 to 150_n may include a plurality of bit line senseamplifiers BLSA. The bit line sense amplifiers BLSA may be implementedas sense amplifier 150 described in FIGS. 1 to 8 .

A plurality of bit line pairs BL and BLB connected to the plurality ofmemory cell arrays 110_1 to 110_n may be respectively connected to theplurality of bit line sense amplifiers BLSA. Memory device 900 has anopen bit line structure. In memory device 900 having an open bit linestructure, when the bit line pair BL and BLB has different capacitances,a sensing operation of the bit line sense amplifier BLSA is disturbedand sensing sensitivity is reduced due to loading mismatch of the bitline pair BL and BLB.

Memory device 900 may include dummy cell arrays 910 and 920 which aredisposed at edges of memory cell arrays 110_1 to 110_n in order toaddress the loading mismatch problem of the bit line pair BL and BLB.Some of bit lines of dummy cell arrays 910 and 920 may be connected toadjacent bit line sense amplifiers BLSA as complementary bit lines. Theremaining bit lines of dummy cell arrays 910 and 920 may not beconnected to the bit line sense amplifiers BLSA as dummy bit lines.

In memory device 900 of FIG. 9 , even when dummy cell arrays 910 and 920are provided, capacitances of the bit line pair BL and BLB may not beequalized. Capacitance imbalance of the bit line pair BL and BLB may actas offset noise of the bit line sense amplifier BLSA. In this case, thebit line sense amplifier BLSA may compensate for a difference due to thecapacitance imbalance of the bit line pair BL and BLB based on theoffset cancelling operation described in FIGS. 1 to 8 .

FIGS. 10 to 17 are diagrams for describing embodiments of layouts andlayout methods of a sense amplifier, such as sense amplifier 150described above with respect to FIGS. 1-8 . FIGS. 10 to 17 eachillustrate a region A of a layout of the plurality of sense amplifiers150_2 of FIG. 9 . In FIGS. 10 to 17 , the pair of PMOS transistors,including first and second PMOS transistors P_1 and P_2, the pair ofNMOS transistors, including first and second NMOS transistors N_1 andN_2, the first and second isolation transistors ISO_1 and ISO_2, and thefirst and second offset cancellation transistors OC_1 and OC_2 of senseamplifier 150, which are illustrated in FIG. 3 , are disposed in one bitline sense amplifier BLSA in plurality of sense amplifiers 150_2.

Referring to FIG. 10 , the bit line sense amplifier BLSA is disposedbetween the bit line BL and the complementary bit line BLB. The pair ofPMOS transistors, i.e., first and second PMOS transistors P_1 and P_2,may be disposed in a central region of the bit line sense amplifierBLSA, and the first NMOS transistor N_1 may be disposed adjacent to thebit line BL and the second NMOS transistor N_2 may be disposed adjacentto the complementary bit line BLB. In this embodiment, the pair of NMOStransistors, i.e., first and second NMOS transistors N_1 and N_2 aredisposed at opposite sides of the bit line sense amplifier BLSA fromeach other, at the edges of bit line sense amplifier BLSA. In thisembodiment, the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2, are disposed in between the pair of NMOStransistors, i.e., first and second NMOS transistors N_1 and N_2.

The first PMOS transistor P_1 may include an active pattern 10 and agate pattern 12 and the second PMOS transistor P_2 may include an activepattern 20 and a gate pattern 22. The first NMOS transistor N_1 mayinclude an active pattern 30 and a gate pattern 32 and the second NMOStransistor N_2 may include an active pattern 40 and a gate pattern 42.

The first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be disposed between the first NMOS transistor N_1and the first PMOS transistor P_1. The first offset cancellationtransistor OC_1 may be disposed adjacent to the first NMOS transistorN_1 and the first isolation transistor ISO_1 may be disposed adjacent tothe first PMOS transistor P_1. The first offset cancellation transistorOC_1 and the first isolation transistor ISO_1 may share a common activepattern 50, and having corresponding gate patterns 51 and 52,respectively.

The second offset cancellation transistor OC_2 and the second isolationtransistor ISO_2 may be disposed between the second NMOS transistor N_2and the second PMOS transistor P_2. The second offset cancellationtransistor OC_2 may be disposed adjacent to the second NMOS transistorN_2 and the second isolation transistor ISO_2 may be disposed adjacentto the second PMOS transistor P_2. The second offset cancellationtransistor OC_2 and the second isolation transistor ISO 2 may include anactive pattern 60 and gate patterns 61 and 62, respectively. Gatepatterns 51 and 61 are conductive lines through which offsetcancellation signals OC are transferred and gate patterns 52 and 62 areconductive lines through which isolation signals ISO are transferred.

Referring to FIG. 11 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 10 in that it further includesdummy conductive lines 1110 and 1120. Hereinafter, layouts of bit linesense amplifiers BLSA of FIGS. 11 to 17 will be mainly described ondifferences from the layout of the bit line sense amplifier BLSA of FIG.10 .

In FIG. 11 , dummy conductive lines 1110 and 1120 may be respectivelydisposed between the first PMOS transistor P_1 and the first isolationtransistor ISO_1 and between the second PMOS transistor P_2 and thesecond isolation transistor ISO_2.

The first and second PMOS transistors P_1 and P_2 which are P-typetransistors and the first and second isolation transistors ISO 1 and ISO2 which are N-type transistors are separated from each other by aprocess design rule, and respective distances between the first andsecond PMOS transistors P_1 and P_2 and the first and second isolationtransistors ISO_1 and ISO_2 may be greater than respective distancesbetween the first and second NMOS transistors N_1 and N_2 and the firstand second offset cancellation transistors OC_1 and OC_2, which are thesame N-type transistors. A difference between the respective distancesmay act as a step in a subsequent wiring process of the bit line senseamplifier BLSA. A region in which such a step is formed may causesensing imbalance of the bit line sense amplifier BLSA.

In order to prevent the sensing imbalance of the bit line senseamplifier BLSA, dummy conductive lines 1110 and 1120 may be respectivelydisposed between the first and second PMOS transistors P_1 and P_2 andthe first and second isolation transistors ISO 1 and ISO 2.

Referring to FIG. 12 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 10 in that the first offsetcancellation transistor OC_1 and the first isolation transistor ISO 1between the first NMOS transistor N_1 and the first PMOS transistor P_1are switched with each other and the second offset cancellationtransistor OC_2 and the second isolation transistor ISO 2 between thesecond NMOS transistor N_2 and the second PMOS transistor P_2 areswitched with each other.

The first isolation transistor ISO_1 may be disposed adjacent to thefirst NMOS transistor N_1 and the first offset cancellation transistorOC_1 may be disposed adjacent to the first PMOS transistor P_1. Thesecond isolation transistor ISO_2 may be disposed adjacent to the secondNMOS transistor N_2 and the second offset cancellation transistor OC_2may be disposed adjacent to the second PMOS transistor P_2.

Referring to FIG. 13 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 12 in that it further includesdummy conductive lines 1310 and 1320. Dummy conductive lines 1310 and1320 are respectively disposed between the first PMOS transistor P_1 andthe first offset cancellation transistor OC_1 and between the secondPMOS transistor P_2 and the second offset cancellation transistor OC_2.

Referring to FIG. 14 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 10 in that pair of NMOStransistors, i.e., the first and second NMOS transistors N_1 and N_2,may be disposed in a central region of the bit line sense amplifierBLSA, and the first PMOS transistor P_1 may be disposed adjacent to thebit line BL and the second PMOS transistor P_2 may be disposed adjacentto the complementary bit line BLB. In this embodiment, the pair of PMOStransistors, i.e., first and second PMOS transistors P_1 and P_2 aredisposed at opposite sides of the bit line sense amplifier BLSA fromeach other, at the edges of bit line sense amplifier BLSA. In thisembodiment, the pair of NMOS transistors, i.e., first and second NMOStransistors N_1 and N_2, are disposed in between the pair of PMOStransistors, i.e., first and second PMOS transistors P_1 and P_2.

The first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be disposed between the first PMOS transistor P_1and the first NMOS transistor N_1. The first offset cancellationtransistor OC_1 may be disposed adjacent to the first PMOS transistorP_1 and the first isolation transistor ISO_1 may be disposed adjacent tothe first NMOS transistor N_1.

The second offset cancellation transistor OC_2 and the second isolationtransistor ISO_2 may be disposed between the second PMOS transistor P_2and the second NMOS transistor N_2. The second offset cancellationtransistor OC_2 may be disposed adjacent to the second PMOS transistorP_2 and the second isolation transistor ISO_2 may be disposed adjacentto the second NMOS transistor N_2.

Referring to FIG. 15 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 14 in that it further includesdummy conductive lines 1510 and 1520. Dummy conductive lines 1510 and1520 may be respectively disposed between the first PMOS transistor P_1and the first offset cancellation transistor OC_1 and between the secondPMOS transistor P_2 and the second offset cancellation transistor OC_2.

In some embodiments, dummy conductive lines 1510 and 1520 may berespectively disposed between the first NMOS transistor N_1 and thefirst isolation transistor ISO 1 and between the second NMOS transistorN_2 and the second isolation transistor ISO 2.

Referring to FIG. 16 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 14 in that the first offsetcancellation transistor OC_1 and the first isolation transistor ISO 1between the first PMOS transistor P_1 and the first NMOS transistor N_1are switched with each other and the second offset cancellationtransistor OC_2 and the second isolation transistor ISO 2 between thesecond PMOS transistor P_2 and the second NMOS transistor N_2 areswitched with each other.

The first isolation transistor ISO_1 may be disposed adjacent to thefirst PMOS transistor P_1 and the first offset cancellation transistorOC_1 may be disposed adjacent to the first NMOS transistor N_1. Thesecond isolation transistor ISO_2 may be disposed adjacent to the secondPMOS transistor P_2 and the second offset cancellation transistor OC_2may be disposed adjacent to the second NMOS transistor N_2.

Referring to FIG. 17 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 16 in that it further includesdummy conductive lines 1710 and 1720. Dummy conductive lines 1710 and1720 may be respectively disposed between the first PMOS transistor P_1and the first isolation transistor ISO_1 and between the second PMOStransistor P_2 and the second isolation transistor ISO_2.

In some embodiments, dummy conductive lines 1710 and 1720 may berespectively disposed between the first NMOS transistor N_1 and thefirst offset cancellation transistor OC_1 and between the second NMOStransistor N_2 and the second offset cancellation transistor OC_2.

In the various embodiments of layouts as described above with respect toFIGS. 10-17 , either: the NMOS transistors are disposed at oppositesides of the sense amplifier from each other, and the PMOS transistorsare disposed in a central region of the sense amplifier between the NMOStransistors, or the PMOS transistors are disposed at the opposite sidesof the sense amplifier from each other, and the NMOS transistors aredisposed in the central region of the sense amplifier between the PMOStransistors.

FIG. 18 is a circuit diagram for describing another embodiment of asense amplifier.

Referring to FIG. 18 , a sense amplifier 150 a further includes anequalizer 1810 as compared to sense amplifier 150 of FIG. 3 .Hereinafter, a difference between sense amplifier 150 a of FIG. 18 andsense amplifier 150 of FIG. 3 will be mainly described.

Equalizer 1810 includes an equalizing transistor EQ connected between asensing bit line SABL and a precharge voltage line carrying theprecharge voltage Vpre. A gate of the equalizing transistor EQ isconnected to an equalizing control line carrying an equalizing signalPEQ.

Equalizer 1810 may equalize a bit line pair BL and BLB and a sensing bitline pair SABL and SABLB to the precharge voltage Vpre. For example,during a pre-charging operation of sense amplifier 150 a, the bit linepair BL and BLB and the sensing bit line pair SABL and SABLB may beconnected to one node when isolation signals ISO and offset cancellationsignals OC are logic high (H). In this case, equalizer 1810 may chargeand equalize the bit line pair BL and BLB and the sensing bit line pairSABL and SABLB to the precharge voltage Vpre in response to theequalizing signal PEQ having a logic high (H) level.

FIGS. 19 and 20 are diagrams for describing embodiments of layouts andlayout methods of sense amplifier of FIG. 18 . A layout of the senseamplifier of FIGS. 19 and 20 corresponds to a region A of the layouts ofthe bit line sense amplifiers BLSA in the plurality of sense amplifiers150_2 described in FIG. 9 , and a difference from the layout of thesense amplifier of FIG. 10 will be mainly described.

Referring to FIG. 19 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 10 in that an equalizingtransistor EQ is further disposed between the first PMOS transistor P_1and the first isolation transistor ISO_1. The equalizing transistor EQmay include an active pattern 50 a and a gate pattern 53. One side ofactive pattern 50 a may be in contact with the common active pattern 50of the first offset cancellation transistor OC_1 and the first isolationtransistor ISO 1 and the precharge voltage Vpre may be applied toanother side of active pattern 50 a via a precharge voltage line. Gatepattern 53 is a conductive equalizing control line through which anequalizing signal PEQ is transferred.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 19 ,the first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be switched with each other and the second offsetcancellation transistor OC_2 and the second isolation transistor ISO_2may be switched with each other.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 19 ,the pair of NMOS transistors, i.e., the first and second NMOStransistors N_1 and N_2 may be disposed in a central region of the bitline sense amplifier BLSA, and the first PMOS transistor P_1 may bedisposed adjacent to the bit line BL and the second PMOS transistor P_2may be disposed adjacent to the complementary bit line BLB. In suchembodiments, the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2 may be disposed at opposite sides of the bitline sense amplifier BLSA from each other, at the edges of bit linesense amplifier BLSA. In such embodiments, the pair of NMOS transistors,i.e., first and second NMOS transistors N_1 and N_2, may be disposed inbetween the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2.

Referring to FIG. 20 , a bit line sense amplifier BLSA differs from thebit line sense amplifier BLSA of FIG. 19 in that it further includesdummy conductive lines 2010 and 2020. Dummy conductive lines 2010 and2020 may be respectively disposed between the first PMOS transistor P_1and the equalizing transistor EQ and between the second PMOS transistorP_2 and the second isolation transistor ISO 2.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 20 ,the first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be switched with each other and the second offsetcancellation transistor OC_2 and the second isolation transistor ISO_2may be switched with each other.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 20 ,the pair of NMOS transistors, i.e., the first and second NMOStransistors N_1 and N_2 may be disposed in a central region of the bitline sense amplifier BLSA, and the first PMOS transistor P_1 may bedisposed adjacent to the bit line BL and the second PMOS transistor P_2may be disposed adjacent to the complementary bit line BLB. In suchembodiments, the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2 may be disposed at opposite sides of the bitline sense amplifier BLSA from each other, at the edges of bit linesense amplifier BLSA. In such embodiments, the pair of NMOS transistors,i.e., first and second NMOS transistors N_1 and N_2, may be disposed inbetween the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2.

FIG. 21 is a circuit diagram for describing still another embodiment ofa sense amplifier.

Referring to FIG. 21 , as compared to sense amplifier 150 a of FIG. 18 ,a sense amplifier 150 b has an equalizer 2110 connected between acomplementary sensing bit line SABL and a precharge voltage linecarrying the precharge voltage Vpre.

Equalizer 2110 may equalize a bit line pair BL and BLB and a sensing bitline pair SABL and SABLB to the precharge voltage Vpre. For example,during a pre-charging operation of sense amplifier 150 b, the bit linepair BL and BLB and the sensing bit line pair SABL and SABLB may beconnected to one node when isolation signals ISO and offset cancellationsignals OC are logic high (H). In this case, equalizer 2110 may chargeand equalize the bit line pair BL and BLB and the sensing bit line pairSABL and SABLB to the precharge voltage Vpre in response to anequalizing signal PEQ of logic high (H).

FIGS. 22 and 23 are diagrams for describing embodiments of layouts andlayout methods of the sense amplifier of FIG. 21 .

Referring to FIG. 22 , a bit line sense amplifier BLSA has an equalizingtransistor EQ disposed between the second PMOS transistor P_2 and thesecond isolation transistor ISO_2 as compared to the bit line senseamplifier BLSA of FIG. 19 . The equalizing transistor EQ may include anactive pattern 60 a and a gate pattern 63. One side of active pattern 60a may be in contact with active pattern 60 of FIG. 10 and a prechargevoltage Vpre may be applied to another side of active pattern 60 a via aprecharge voltage line. Gate pattern 63 is a conductive equalizingcontrol line through which an equalizing signal PEQ is transferred.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 22 ,the first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be switched with each other and the second offsetcancellation transistor OC_2 and the second isolation transistor ISO_2may be switched with each other.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 22 ,the pair of NMOS transistors, i.e., the first and second NMOStransistors N_1 and N_2 may be disposed in a central region of the bitline sense amplifier BLSA, and the first PMOS transistor P_1 may bedisposed adjacent to the bit line BL and the second PMOS transistor P_2may be disposed adjacent to the complementary bit line BLB. In suchembodiments, the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2 may be disposed at opposite sides of the bitline sense amplifier BLSA from each other, at the edges of bit linesense amplifier BLSA. In such embodiments, the pair of NMOS transistors,i.e., first and second NMOS transistors N_1 and N_2, may be disposed inbetween the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2.

Referring to FIG. 23 , a bit line sense amplifier BLSA further includesdummy conductive lines 2310 and 2320 as compared to the bit line senseamplifier BLSA of FIG. 22 . Dummy conductive lines 2310 and 2320 may berespectively disposed between the first PMOS transistor P_1 and thefirst isolation transistor ISO_1 and between the second PMOS transistorP_2 and the equalizing transistor EQ.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 23 ,the first offset cancellation transistor OC_1 and the first isolationtransistor ISO_1 may be switched with each other and the second offsetcancellation transistor OC_2 and the second isolation transistor ISO_2may be switched with each other.

In some embodiments, in the bit line sense amplifier BLSA of FIG. 23 ,the pair of NMOS transistors, i.e., the first and second NMOStransistors N_1 and N_2, may be disposed in a central region of the bitline sense amplifier BLSA, and the first PMOS transistor P_1 may bedisposed adjacent to the bit line BL and the second PMOS transistor P_2may be disposed adjacent to the complementary bit line BLB. In suchembodiments, the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2 may be disposed at opposite sides of the bitline sense amplifier BLSA from each other, at the edges of bit linesense amplifier BLSA. In such embodiments, the pair of NMOS transistors,i.e., first and second NMOS transistors N_1 and N_2, may be disposed inbetween the pair of PMOS transistors, i.e., first and second PMOStransistors P_1 and P_2.

In the various embodiments of layouts as described above with respect toFIGS. 19, 20, 22 and 23 , either: the NMOS transistors are disposed atopposite sides of the sense amplifier from each other, and the PMOStransistors are disposed in a central region of the sense amplifierbetween the NMOS transistors, or the PMOS transistors are disposed atthe opposite sides of the sense amplifier from each other, and the NMOStransistors are disposed in the central region of the sense amplifierbetween the PMOS transistors.

FIGS. 24 and 25 are diagrams illustrating example embodiments of amemory device to which a sense amplifier as described herein may beapplied. FIGS. 24 and 25 are diagrams illustrating portionscorresponding to first and second memory cell arrays 110_1 and 110_2 andsecond sense amplifiers 150_2, which are some portions of plurality ofmemory cell arrays 110_1 to 110_n and plurality of sense amplifiers150_1 to 150_n described above in FIG. 9 . Each of second senseamplifiers 150_2 may include a plurality of bit line sense amplifiersBLSA. The bit line sense amplifiers BLSA may be implemented as senseamplifiers 150, 150 a, or 150 b described in FIGS. 1 to 23 .

In a memory device 2400 of FIG. 24 , two bit line sense amplifiers BLSAin second sense amplifiers 150_2 a are disposed adjacent to each other,unlike in memory device 900 of FIG. 9 . The two bit line senseamplifiers BLSA may be connected to first and second bit lines BL1 andBL2 and first and second complementary bit lines BLB1 and BLB2. One ofthe two bit line sense amplifiers BLSA may sense a voltage variationbetween the first bit line pair BL1 and BLB1 and the other thereof maysense a voltage variation between the second bit line pair BL2 and BLB2.

In a memory device 2500 of FIG. 25 , three bit line sense amplifiersBLSA 3 in second sense amplifiers 150_2 b are disposed adjacent to oneanother, unlike in memory device 900 of FIG. 9 . The three bit linesense amplifiers BLSA may be connected to first to third bit lines BL1to BL3 and first to third complementary bit lines BLB1 to BLB3. Each ofthe three bit line sense amplifiers BLSA may sense a voltage variationbetween each of the first to third bit line pairs (BL1 and BLB1), (BL2and BLB2), and (BL3 and BLB3).

Memory devices 2400 and 2500 of FIGS. 24 and 25 may be selectivelyapplied according to a trend, in which a size of a unit cell is reduced,due to miniaturization in a design rule caused by the highly integratedmemory cell device. In some embodiments, n bit line sense amplifiersBLSA may be disposed adjacent to each other, the n bit line senseamplifiers BLSA may be connected to first to n^(th) bit lines BL1 to BLnand first to n^(th) complementary bit lines BLB1 to BLBn, and each ofthe n bit line sense amplifiers BLSA may sense a voltage variation ofeach of first to n^(th) bit line pairs (BL1 and BLB1) to (BLn and BLBn).

In memory devices 2400 and 2500, a plurality of bit line senseamplifiers BLSA arranged in a matrix, including a plurality of rows eachextending between first memory cell array 110_1 and second memory cellarray 110_2 along a first direction, and a plurality of columns eachextending along a second direction which is perpendicular to the firstdirection. At least one of the rows and at least one of the columns eachincludes more than one of the plurality of bit line sense amplifiersBLSA, and typically there may be multiple bit line sense amplifiers BLSAin each row and in each column.

FIG. 26 is a block diagram illustrating an example embodiment in which amemory device including a sense amplifier as described herein is appliedto a mobile device. The mobile device may be a mobile phone or a smartphone.

Referring to FIG. 26 , a mobile device 2600 includes a Global System forMobile Communications (GSM) block 2610, a near-field communication (NFC)transceiver 2620, an input-and-output block 2630, an application block2640, a memory 2650, and a display 2660. The components or blocks ofmobile device 2600 in FIG. 26 are illustrated as examples. Mobile device2600 may include more or fewer components or blocks. Also, although thecomponents or blocks using GSM technology are illustrated in the presentembodiment, mobile device 2600 may be implemented using othertechnologies such as code division multiple access (CDMA). The blocks ofFIG. 26 may be implemented in the form of an integrated circuit.Alternatively, while some of the blocks may be implemented in the formof an integrated circuit, other blocks may be implemented in a separateform.

GSM block 2610 may be connected to an antenna 2611 and may operate toprovide operations of a wireless phone in a known manner. GSM block 2610may include a receiver and a transmitter therein and performcorresponding receiving and transmitting operations.

NFC transceiver 2620 may be configured to transmit and receive NFCsignals using inductive coupling for wireless communication. NFCtransceiver 2620 may provide the NFC signals to an NFC antenna matchingnetwork system 2621 and the NFC antenna matching network system 2621 maytransmit the NFC signals using inductive coupling. The NFC antennamatching network system 2621 may receive NFC signals provided fromanother NFC device and provide the received NFC signals to NFCtransceiver 2620.

Application block 2640 may include hardware circuits, for example, oneor more processors and may operate to provide various user applicationsprovided by mobile device 2600. The user applications may include voicecall operations, data transmission, data swapping, and the like.Application block 2640 may operate in conjunction with GSM block 2610and/or NFC transceiver 2620 and provide operation characteristics of GSMblock 2610 and/or NFC transceiver 2620. Alternatively, application block2640 may include a program for mobile point of sale (POS). Such aprogram may provide a credit card purchase and payment function using amobile phone, e.g., a smart phone.

Display 2660 may display an image in response to display signalsreceived from application block 2640. The image may be provided fromapplication block 2640 or may be generated by a camera embedded inmobile device 2600. Display 2660 may include a frame buffer therein fortemporarily storing pixel values, and may be configured as a liquidcrystal display screen with associated control circuits.

Input-and-output block 2630 provides an input function to a user, andprovides outputs to be received through application block 2640.

Memory 2650 may store programs (instructions) and/or data to be used byapplication block 2640, and may be implemented as a random-access memory(RAM), a read-only memory (ROM), a flash memory, or the like. Therefore,memory 2650 may include non-volatile memory devices as well as volatilememory devices. For example, memory 2650 may correspond to memory device100, 900, 2400, or 2500 described in FIGS. 1 to 25 .

Memory 2650 may include a sense amplifier for improving an effectivesensing margin based on an operation of cancelling an offset of thesense amplifier. The sense amplifier may include a sense amplifyingunit, a first isolation unit, a second isolation unit, a first offsetcancellation unit, and a second offset cancellation unit, and the senseamplifying unit may include a first PMOS transistor, a second PMOStransistor, a first NMOS transistor, and a second NMOS transistor.

In some embodiments of memory 2650, the pair of PMOS transistors, i.e.,the first and second PMOS transistors may be disposed in a centralregion of the sense amplifier, the pair of NMOS transistors, i.e., thefirst and second NMOS transistors may be respectively disposed atopposite sides of the sense amplifier from each other, the firstisolation unit and the first offset cancellation unit may be disposedbetween the first PMOS transistor and the first NMOS transistor, and thesecond isolation unit and the second offset cancellation unit may bedisposed between the second PMOS transistor and the second NMOStransistor.

In other embodiments of memory 2650, the pair of NMOS transistors, i.e.,the first and second NMOS transistors may be disposed in a centralregion of the sense amplifier, the pair of PMOS transistors, i.e., thefirst and second PMOS transistors may be respectively disposed atopposite sides of the sense amplifier from each other, the firstisolation unit and the first offset cancellation unit may be disposedbetween the first NMOS transistor and the first PMOS transistor, and thesecond isolation unit and the second offset cancellation unit may bedisposed between the second NMOS transistor and the second PMOStransistor.

While the inventive concept has been particularly shown and describedwith reference to embodiments thereof, it will be understood thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

What is claimed is:
 1. A method of operating a sense amplifier fordynamic random access memory (DRAM) device, the method comprising:performing a pre-charging operation on a bit line pair and a sensing bitline pair while maintaining an isolation signal and an offsetcancellation signal logic high, the bit line pair comprising a bit lineand a complementary bit line and the sensing bit line pair comprising asensing bit line and a complementary sensing bit line; performing anoffset cancelling operation by transitioning the isolation signal logiclow and transitioning a first control signal from a first prechargevoltage to an internal supply voltage, and transitioning a secondcontrol signal from the first precharge voltage to a ground voltage;performing a charge sharing operation by transitioning the offsetcancellation signal logic low and activating a word line, therebysharing charges stored in a memory cell coupled to the word line withthe bit line and transitioning both the first control signal and thesecond control signal to the first precharge voltage; performing apre-sensing operation by transitioning the first control signal to theinternal supply voltage, and transitioning the second control signal tothe ground voltage, thereby sensing operation being performed on thesensing bit line pair; and performing a restoring operation bytransitioning the isolation signal logic high, thereby connecting thebit lines pairs and the sensing bit line pair, wherein the senseamplifier comprises: first isolation transistor configured to connectthe bit line to the sensing bit line in response to the isolationsignal; second isolation transistor configured to connect thecomplementary bit line to the complementary sensing bit line in responseto the isolation signal; first offset compensation transistor configuredto connect the bit line to the complementary sensing bit line inresponse to the offset cancellation signal; second offset compensationtransistor configured to connect the complementary bit line to thesensing bit line in response to the offset cancellation signal; and asense amplifying unit configured to sense and amplify a voltagedifference between the bit line and the complementary bit line, thesense amplifying unit including first and second P-type metal oxidesemiconductor (PMOS) transistors and first and second N-type metal oxidesemiconductor (NMOS) transistors, wherein the first isolation transistorand the first offset compensation transistor are disposed between thefirst PMOS transistor and the first NMOS transistor, and the secondisolation transistor and the second offset compensation transistor aredisposed between the second PMOS transistor and the second NMOStransistor.
 2. The method of claim 1, wherein the first and secondisolation transistors are turned-on when the isolation signal is logichigh and connect the bit line pair to the sensing bit line pair.
 3. Themethod of claim 1, wherein the first offset compensation transistor isturned-on when the offset cancellation signal is logic high forconnecting the bit line to the complementary sensing bit line, and thesecond offset compensation transistor is turned-on when the offsetcancellation signal is logic high for connecting the complementary bitline to the sensing bit line.
 4. The method of claim 3, wherein theoffset canceling operation cancels offset voltage of the sense amplifierby forming a voltage difference on the bit line pairs and the sensingbit line pairs that cancels the offset voltage.
 5. The method of claim1, wherein the sense amplifier further comprising an equalizer connectedbetween a precharge voltage line and one of the sensing bit line and thecomplementary sensing bit line for precharging the sensing bit line andthe complementary sensing bit line.
 6. The method of claim 5, whereinthe equalizer is disposed between the first PMOS transistor and thefirst NMOS transistor.
 7. The method of claim 1, wherein the isolationtransistor and the offset compensation transistor share a common activepattern, and each has a corresponding gate pattern.
 8. The method ofclaim 1, wherein the first control signal is connected to source nodesof the first and second PMOS transistors.
 9. The method of claim 1,wherein the second control signal is connected to source nodes of thefirst and second NMOS transistors.
 10. The method of claim 1, whereinthe first precharge voltage is substantially half level of the internalsupply voltage.
 11. A method of operating a sense amplifier for dynamicrandom access memory (DRAM) device, the method comprising: performing apre-charging operation on a bit line pair and a sensing bit line pairwhile maintaining an isolation signal and an offset cancellation signallogic high, the bit line pair comprising a bit line and a complementarybit line and the sensing bit line pair comprising a sensing bit line anda complementary sensing bit line; performing an offset cancellingoperation by transitioning the isolation signal logic low andtransitioning a first control signal from a first precharge voltage toan internal supply voltage, and transitioning a second control signalfrom the first precharge voltage to a ground voltage; performing acharge sharing operation by transitioning the offset cancellation signallogic low and activating a word line, thereby sharing charges stored ina memory cell coupled to the word line with the bit line andtransitioning both the first control signal and the second controlsignal to the first precharge voltage; performing a pre-sensingoperation by transitioning the first control signal to the internalsupply voltage, and transitioning the second control signal to theground voltage, thereby sensing operation being performed on the sensingbit line pair; and performing a restoring operation by transitioning theisolation signal logic high, thereby connecting the bit lines pairs andthe sensing bit line pair, wherein the sense amplifier comprises: afirst set including a first dummy conductive line, a first PMOStransistor, a first NMOS transistor, a first isolation transistor and afirst offset cancellation transistor, and the first dummy conductiveline being disposed adjacent to the first PMOS transistor, wherein thefirst dummy conductive line, the first isolation transistor and thefirst offset cancellation transistor are disposed between the first PMOStransistor and the first NMOS transistor; and a second set including asecond dummy conductive line, a second PMOS transistor, a second NMOStransistor, a second isolation transistor and a second offsetcancellation transistor, and the second dummy conductive line beingdisposed adjacent to the second PMOS transistor, wherein the seconddummy conductive line, the second isolation transistor and the secondoffset cancellation transistor are disposed between the second PMOStransistor and the second NMOS transistor, wherein the first set andsecond set are disposed symmetrically.
 12. The method of claim 11,wherein the first and second isolation transistors are turned-on whenthe isolation signal is logic high and connect the bit line pair to thesensing bit line pair.
 13. The method of claim 11, wherein the firstoffset compensation transistor is turned-on when the offset cancellationsignal is logic high for connecting the bit line to the complementarysensing bit line, and the second offset compensation transistor isturned-on when the offset cancellation signal is logic high forconnecting the complementary bit line to the sensing bit line.
 14. Themethod of claim 13, wherein the offset canceling operation cancelsoffset voltage of the sense amplifier by forming a voltage difference onthe bit line pairs and the sensing bit line pairs that cancels theoffset voltage.
 15. The method of claim 11, wherein the sense amplifierfurther comprising an equalizer connected between a precharge voltageline and one of the sensing bit line and the complementary sensing bitline for precharging the sensing bit line and the complementary sensingbit line.
 16. The method of claim 15, wherein the equalizer is disposedbetween the first PMOS transistor and the first NMOS transistor.
 17. Themethod of claim 11, wherein the isolation transistor and the offsetcompensation transistor share a common active pattern, and each has acorresponding gate pattern.
 18. The method of claim 11, wherein thefirst control signal is connected to source nodes of the first andsecond PMOS transistors.
 19. The method of claim 11, wherein the secondcontrol signal is connected to source nodes of the first and second NMOStransistors.
 20. The method of claim 11, wherein the first prechargevoltage is substantially half level of the internal supply voltage.